This invention relates to fault tolerant arrangements for synchronous machines such as synchronous motors or generators by which a high power synchronous machine is permitted to operate at lower power under faulted or grounded stator winding conditions.
The prior art does not disclose ways to permit continued lower power operation of a high power synchronous machine having faulted windings. In the Zorzi U.S. Pat. No. 1,908,620 a motor generator structure has a non-magnetic sleeve with inserts of magnetic material which are incorporated into the machine when it is assembled. There is no provision for compensating for faults in the windings in the machine.
The Surjaninoff U.S. Pat. No. 2,128,544 discloses a sleeve in the gap between the stator and the rotor of an electric motor which is made of an insulating binder material incorporating finely divided magnetic material in which the distribution of magnetic material varies throughout the sleeve to minimize flux leakage while maximizing coupling between the stator coils and the rotor. The patent to Taiani U.S. Pat. No. 4,396,849 describes a synchronous magnetic drive having a non-metallic sleeve positioned in the gap between the rotor and the stator to reduce current losses and the patent to Morrison et al. U.S. Pat. No. 5,550,417 discloses the use of electrically conductive inserts for altering the response of motor and generator structures.
Accordingly, it is an object of the present invention to provide a synchronous machine having fault tolerance which overcomes disadvantages of the prior art.
Another object of the invention is to provide a synchronous machine in which faults in stator windings can be compensated to permit continued operation of the machine.
These and other objects of the invention are attained by providing a synchronous machine having a non-magnetic sleeve installed in the air gap between the rotor and the stator of the machine and affixed to the stator in which slots are arranged to selectively receive segments of a high permeability magnetic material so that, when a stator winding fault occurs, one or more sets of segments of high permeability magnetic material can be inserted into appropriate slots to provide low reluctance shunt paths for magnetic flux from the affected windings of the faulted phase or phases, thereby minimizing flux linkage between those windings and the rotor field. This minimizes the internally generated phase voltages and consequent fault currents.